INT 10 - VIDEO - FIND PIXEL VALUE (Hercules GRAFIX)
        AH = 47h
        DI = x (0-720)
        BP = y (0-347)
Return: AL = 00h pixel clear
        AL = 01h pixel set
Note:   function 43h specifies which page is used
SeeAlso: AH=0Dh,AH=46h

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